1. Field of the Invention
This invention relates to a process for producing the diphenylamines or N,N'-diphenyl-phenylenediamines. More specifically, this invention relates to a process for producing the diphenylamines or N,N'-diphenyl-phenylenediamines by heat-reacting an aniline or a phenylenediamine with a phenol in the presence of a hydrogen transfer catalyst and a cyclohexanone corresponding to said phenol, using the phenol in an excessive amount to the aniline or phenylenediamine.
2. Background Art
In the past, the known processes for producing the diphenylamines include that in which the diphenylamines are produced by a deammoniation reaction from such amines as aniline or that in which the diphenylamines are produced by either a dehydration or dehydrobromination reaction from amines and phenols or bromobenzene. As specific suggestions, there has been proposed a process for producing a diphenylamine from a phenol and aniline using gamma-alumina as catalyst (Japanese Patent Publication No. 14738/1974), and a process involving acetylation of 2-methyl-4-methoxyaniline, reacting the resultant product with bromobenzene, and thereafter hydrolyzing the resulting 2-methyl-4-methoxy-N-acetyldiphenylamine to give 2-methyl-4-methoxydiphenylamine (Japanese Patent Publication No. 5489/1977).
On the other hand, as processes for producing the N-alkyldiphenylamines, known are such processes as that wherein a diphenylamine is reacted with an alkyl halide, dialkyl sulfate or trialkyl phosphate, and that in which a hydrochloride of diphenylamine and alcohol are reacted. And as the process for producing the N,N'-diphenyl-phenylenediamines, known is that in which phenylenediamine, dihydroxybenzene or disulfoxybenzene, and aniline or a salt thereof are reacted.
All of the foregoing processes are however extremely unsatisfactory for use as industrial processes.
As a process differing from the foregoing processes, also known is a process which involves reacting an amine with a Schiff base. Specifically, there has been suggested a process involving reaction N-cyclohexylideneaniline in the vapor phase with an oxygen-containing gas in the presence of an oxidizing catalyst such as silica (Japanese Laid-Open Patent Publication No. 49,924/1974), or a process which comprises heat-reacting N-methylaniline and cyclohexanone in the presence of a palladium catalyst and thereafter submitting the resulting Schiff base to a dehydrogenation reaction to give N-methyldiphenylamine (U.S. Pat. No. 3,219,704). The dehydrogenation reaction of these processes are however carried out in the absence of a hydrogen acceptor, with the consequence that the yields are unsatisfactory low values despite the fact that the N-methylaniline and cyclohexanone are used in nearly equivalent ratio.
Further, there has also been suggested a process which uses a styrene as the hydrogen acceptor in producing diphenylamines via a Schiff base such as N-cyclohexylideneaniline by reacting an amine with a cyclohexanone in the presence of a hydrogenating catalyst such as a palladium catalyst (Japanese Laid-Open Patent Publication No. 58,648/1982).
Specifically, this process is a process for obtaining 4-aminodiphenylamine from p-phenylenediamine. This process is on the whole satisfactory as regards its reaction rate and selectivity. However, for obtaining the intended product this process requires the use of an aniline and a substantially equivalent amount of a cyxlohexanone. And the not readily available cyclohexanones must be synthesized from the phenols in a separate step. Further, the styrenes are only utilized as a hydrogen acceptor. This process thus cannot be regarded as being an industrially satisfactory process for producing the diphenylamines.
If a more detailed description is made, in the process of the foregoing Japanese Laid-Open Patent Publication No. 58,648/1982 the styrene added as a hydrogen acceptor becomes catalytically hydrogenated to become an entirely different compound that cannot be incorporated into the reaction system of this process, and it thus cannot be recycled for reuse. Hence, unless there can be conceived an effective use for this compound, the process becomes extremely costly when applied industrially. Further, since the styrene, as described above, becomes catalytically hydrogenated to become an entirely different compound that cannot be incorporated into the reaction system of this process, the proportion in which the amines and cyclohexanones used must be brought as close as possible to the equivalent ratio. Otherwise, a separate step for separating and purifying the excess amines and/or cyclohexanones will be required, or a loss in the amines or cyclohexanones will be brought about.